1. Field of the Invention
The present invention relates to an image display device.
2. Description of the Related Art
According to laser elements serving as a light source for projecting and displaying images in projection televisions, output characteristics and the life of the laser element used (a semiconductor laser element) are influenced largely by its operating temperature. Therefore, the temperature needs to be managed to stabilize an output. The projection television includes a cooling device that cools the laser element for maintaining the operating temperature thereof to be constant.
Japanese Patent Application Laid-open No. H10-335724 describes that, in a temperature control circuit of a semiconductor laser, a current flows in a Peltier device for cooling or heating the semiconductor laser based on a temperature of the semiconductor laser detected by a thermistor.
However, Japanese Patent Application Laid-open No. H10-335724 does not describe what control is performed when an environmental temperature is higher than expected or when the Peltier device has some failures and thus its cooling capacity is reduced.
Meanwhile, the projection television (image display device) sometimes includes a heat pipe, a radiating radiator, and a fan in a Peltier device unit for radiation. In this case, depending on an actual usage environment, a sufficient air path for the fan cannot be ensured or the radiator and the fan are clogged with dust, thus the amount of heat cooled by the Peltier device unit may be reduced. That is, the cooling capacity of the Peltier device unit is reduced and the temperature of the laser element may not be controlled to a target temperature. When the laser element continues to be used at a high temperature exceeding the target temperature, the laser element is broken or its life is shortened.